This invention relates generally to a system for raising and lowering antennae and related equipment used in cellular telecommunications systems and in PCS (personal communications systems). In particular, the invention relates to a mast pole shaft which is provided with a ring or platform assembly that is raised and lowered by use of lift cables that are operatively connected to a hoisting means located in the lower portion of the mast pole shaft through a transition assembly provided in association therewith. The system of the present invention provides means for guiding lift cables and telecommunications cables, e.g., coaxial signal cables and power cables, during raising and lowering of the antennae and related equipment.
Prior art mast pole systems used in connection with the operation of wireless cellular telecommunications systems require that antennae used as part of such telecommunications equipment be permanently affixed at an elevated position near the top of a mast tower, tubular pole or similar lattice structure. Typically, multiple antennae are affixed near the top of the mast tower, each antenna having an associated coaxial signal cable connecting it with ground-positioned ancillary equipment. In order to enable service personnel to provide maintenance to these pole mounted antennae, steps, ladders or other climb facilitating means are commonly permanently attached to the pole provided so that they extend from near ground level to the elevated position where the antennae are located. Additionally, safety regulations require that current technology mast poles be provided with safety climbing equipment and a service platform mounted at the elevated position where antennae and other related telecommunications equipment are located to enable safe performance of service work by service personnel.
Many in industry and public have considered the presence of such permanently mounted climb facilitating means and safety platforms on a communications pole to detract from the aesthetic appearance of the site on which the communications pole is located. In fact, the presence of such on a communications pole has been reason enough for rejection of a proposal during a zoning review. Additionally, the installation of steps, safety climbing equipment and safety platforms increases cost of manufacture. Therefore, there has been a long-felt need by the public and those in industry for a communications pole that eliminates the need for steps, safety platforms and safety climbing devices and provides a more streamlined and visually appealing appearance that would be more acceptable to the public and zoning review boards. Additionally, the presence of permanently mounted climb facilitating means presents a potentially serious liability problem in the event a trespasser should suffer an accident as the result of climbing such equipment and falling therefrom.
Since under prior art systems, service can only be performed at the elevated position where the antenna are permanently affixed, safety is a matter of great importance. Only service personnel having specialized training as steeplejacks may be utilized for providing service to pole mounted equipment. Since relatively few service people possess the skills of a steeplejack, such individuals are able to command a higher fee for their services and are usually in great demand and are often not available. Further, while a steeplejack repairman is performing service at an elevated position, under safety requirements, a second service person must be stationed at the base of the pole while the steeplejack is working at an elevated position to provide assistance in the event of an emergency. Therefore, from both a cost and safety standpoint, there has been a long-felt need in the industry for a system that enables service personnel not having the steeplejack skills to perform service work safely.
Additionally, under prior art systems, antennae are customarily mounted at an elevated position on the mast pole while all other related telecommunications equipment, e.g., radio frequency equipment, power supplies, batteries, rectifiers, are positioned at ground level and situated around the base of the pole. By positioning all telecommunications equipment other than antennae at ground level rather than on the mast pole, service may be provided to this equipment without requiring service personnel to climb up the mast pole.
However, positioning such equipment at ground level has several drawbacks. For example, a considerably larger sized lot is required to accommodate this equipment. Further, in order to protect against vandalism and weather, it is not uncommon for the ground stationed equipment to be housed within a trailer or similar sheltering structure which further increases the required lot size and cost. Additionally, it is not uncommon for fencing to be erected around ground stationed equipment to deter vandalism thus further increasing the required lot size and cost. Accordingly, in order to position telecommunications equipment at ground level, a relatively large tract of land must be provided on which a shelter can be located and fencing can be erected in order to house and protect such equipment. Therefore, there is a long-felt need for a system that can be implemented on a smaller tract of land and that can be implemented without the necessity of utilizing the costly protective measures mentioned above.
There are raise/lowering devices in the prior art that are dedicated to the purpose of raising and lowering lighting systems. These lighting systems also known as luminaires. Such raise/lowering devices are manufactured by several different companies including American High Mast, Inc., the assignee of the present invention and application. Such systems have been in existence and commercially available for some time and routinely appear in parking lots, shopping centers, highways, toll plazas, airports and other locations where outdoor illumination is required. Under these prior art lighting raise/lowering devices for lights, a plurality of luminaires are attached to a platform assembly that surrounds the outside of the mast pole. The platform assembly is typically suspended by three lift cables that connect thereto and extend through the interior of the mast pole and connect to a hoisting means, e.g., an internal motor. Additionally, one or at most two power cables connected to the luminaires extend through the mast pole and connect at their second end to power supplies positioned at ground level. However, under these prior art systems, since only three lift cables and one or two power cables actually extended through the interior of the mast pole shaft there was no reason to provide a means for routing these cables or for assuring their proper orientation as they feed out of the mast pole and connect to the luminaires and other related equipment mounted on the platform assembly.
While the prior art raise/lowering devices are adequate for their intended purpose, i.e., raising and lowering luminaires, they are inadequate for raising and lowering antennae and other related telecommunications equipment because these devices provide no means for routing the additional telecommunications cables, e.g., coaxial signal cables and power cables, and lift cables associated with such equipment. Under the prior art, a single large opening is provided at the top of the mast pole through which all cables are fed. This large opening is inadequate for routing and assuring proper orientation for a plurality of telecommunications cables, e.g., multiple coaxial signal cables, a plurality of power cables, in addition to at least six lift cables. Therefore there is a long-felt need for a system for routing a significant number of cables, e.g., telecommunications cables, lift cables.
Under the prior art luminaire raise/lowering devices where such a single large opening is utilized for routing cables, a special dome is typically provided over the large opening for the purpose of protecting against the entry of rain water, birds and bird droppings into the pole.
Further, under prior art raise/lowering systems for luminaires, a mechanical clutch is coupled to the electrical motor for the purpose of controlling the delivery of torque from the motor to the gears. Under these prior art systems, once a predetermined amount of torque is reached, such as when the platform assembly reaches the elevated position and abuts the headframe assembly, the mechanical clutch disengages the motor from the gears in order to discontinue the raising of the platform assembly. Unless a clutch is provided, the motor will continue to exert torque pulling on lift cables and platform assembly. Such torque may damage the motor and/or other system components and eventually result in one or several lift cables being broken away from the platform assembly they are supporting.
Because the clutch is a device that is mechanical in nature, it may fall out of calibration, which can result in damage to the system and the motor. When utilizing a raise/lowering device for raising and lowering expensive telecommunications equipment, there must be provided a more accurate and reliable means for disengaging the motor from the gears once the platform assembly reaches the elevated position and once the platform assembly reaches the lowered position for servicing. Further, there is a need for a means for slowing the ascent and descent of the platform assembly as it approaches the elevated and lowered positions.